This invention relates to limited slip differential axle assemblies of the type including clutch packs for improved traction over a variety of driving conditions. More particularly, the invention relates to a bias control mechanism wherein the effectiveness of the clutch packs may be modulated from zero or full differentiation to maximum or full axle lock-up. The mechanism is electromagnetically and variably controllable by a vehicle operator, preferably from a vehicle control panel or dashboard.
A number of prior art mechanisms provide for bias control of differential axles through clutch packs which provide limited slip action for improved traction in slippery or generally non-dry road conditions. One of such devices provides a variable bias clutch pack which tends to respond more quickly than most conventional types of clutch packs. Another device provides for both zero and full differentiation modes, with a conventional clutch pack limited slip capability in a third mode. However, the latter cannot be modulated. In fact, this inventor is not aware of any modulating bias control systems providing for variation in degree of limited slip action. Such a system would permit choices of specific amounts of bias suitable for a variety of driving situations. The vehicle operator would thus be able to achieve a more desirable and safer operation.
The limited slip differential axle assembly disclosed herein provides a means for bias control at the choice and selection of a vehicle operator over an infinite range of control from zero and no bias through intermediate ranges of bias to full bias or complete axle lock-up.
In a preferred form, the limited slip differential axle assembly includes an electromagnetically actuated coil rigidly affixed to the differential carrier, and oriented radially about the driving axle shafts. Relatively rotatable with respect to the coil is a magnet shell which is rigidly affixed to one part of a two part differential case. The other part of the case supports a loading ring to which an armature is threadably secured to provide an adjustable air gap for control of electromagnetic flux. A differential clutch pack provides two sets of interleaved friction discs, a first set rigidly affixed to one of the side gears of the differential, while the second set forms a part of one of the portions of the two-part differential case.
When the coil is energized, magnetic flux attracts the armature, and will thus tend to pull same toward the magnet shell. This action will result in the loading ring urging a plurality of pressure plate segments against the clutch pack to bias the side gear under a controllable amount of friction drag with respect to the differential case.
By controlling intensity of the electromagnetic flux, preferably from a control panel, an operator will be able to mdoulate bias for any given road condition, ranging from complete lack of bias to achievement of full bias.